The purpose of this investigation is to compare the results of mutagenicity testing using commercial oxidative-type hair dyes as test compounds and Escherichia coli K-12/343/113 as indicator of gene mutations with those results obtained in Salmonella typhimurium. In the latter organism, approximately 90% of the hair dye formulations show genetic activity in inducing reverse mutations in the histidine requiring strain TA1538. To determine the role of mammalian foreign compound metabolism on the mutagenicity of these compounds, extracts of rodent liver will be incubated together with the indicator microbes. The comparison of results between Salmonella and Escherichia will indicate whether the mutagenicity of hair dyes is restricted to specific gene segments or is due to a more universal type of DNA alteration.